1. Field of the Invention
The invention relates to immunoassay devices and methods for collection and assaying of biological fluids, particularly urine. The invention further relates to means for controlling fluid flow through a wicking membrane.
2. History of the Related Art
With the increasing availability and use of drugs by the general population, employers such as government agencies, sports groups and transportation related companies utilize drug screenings as both conditions of employment and maintenance of safety in the workplace. To have a doctor present at the workplace to perform the drug screenings is both expensive and impractical for an employer. Accordingly, other methods have been developed to perform the drug screenings.
One such method is exemplified in U.S. Pat. No. 5,403,551 entitled xe2x80x9cAssaying Device and Container for In Field Analysis of a Specimen and Later Shipment of the Unadulterated Specimen.xe2x80x9d This device is relatively expensive to manufacture because it requires specialized components (particularly a special fluid collection cup), and is relatively complex to operate by laymen, as well as being subject to leakage and contamination.
The invention provides means for controlling assay sample fluid flow through an assay test strip for use in performing immunoassays in a dipstick format. In particular, fluid flow control is accomplished by placing the assay test strip within a flow control channel in which the ambient pressure within the flow control channel is maintained in substantial equilibrium with the ambient pressure outside the flow control channel.
By avoiding the formation of a pressure gradient within the flow control channel along which assay sample fluid would be encouraged to flow into the flow control channel, fluid flow from the sample source into which the dipstick assay test strip is immersed is substantially limited to migration by wicking through the test strip. In this fashion, the risk of oversaturation of the test strip on introduction into an assay sample fluid is minimized. As such, the need for other means of restricting the rate or volume of flow through a dipstick assay test strip, such as a housing with a limited volume sample application port or steps to indirectly introduce sample onto the test strip, is also avoided, thereby reducing manufacturing costs and increasing the speed of assay performance.
The invention further provides a combination assaying device and collection chamber which is capable of easily collecting and testing a biological fluid sample, such as urine, while maintaining the sample unadulterated and secure. In particular, the invention provides a fluid flow control test strip in a chamber on a solid support introduced into a fluid collection chamber, such as a urine cup, wherein the volume capacity of the assay sample fluid collection container is such that the total fluid pressure obtainable within the container is maintained at or below 1 atmosphere.